U.S. patent application number 16/626663 was filed with the patent office on 2020-07-16 for wave powered generator.
The applicant listed for this patent is Marine Power Systems Limited. Invention is credited to Graham Foster.
Application Number | 20200224633 16/626663 |
Document ID | / |
Family ID | 59592607 |
Filed Date | 2020-07-16 |
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United States Patent
Application |
20200224633 |
Kind Code |
A1 |
Foster; Graham |
July 16, 2020 |
Wave Powered Generator
Abstract
A generator for capturing and converting wave energy into a more
useful form is provided. The generator comprises: at least one
energy capturing float (2) which is movable in response to wave
motion; a reaction member (1) to be positioned below the energy
capturing float; connecting lines (5a, 5b, 5c, 5d) for connecting
the at least one energy capturing float to the reaction member and
defining a spacing (D2) between the energy capturing float and the
reaction member; energy convertors (6a, 6b, 6c, 6d) for converting
relative movement between the reaction member and at least one
respective energy capturing float to useful energy. The generator
includes depth setting means such as adjustable mooring lines (3a,
3b, 3c, 3d) securing the reaction member to the sea bed SB for
setting the depth (D1) of the reaction member in the sea. Both the
float and the reaction member possess a positive buoyancy, allowing
suitable tension to be applied to the mooring lines. The improved
tension brought about by the net positive buoyancy has the
surprising effect of improved stability in energetic sea
conditions.
Inventors: |
Foster; Graham; (Swansea,
South Wales, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Marine Power Systems Limited |
Swansea, South Wales |
|
GB |
|
|
Family ID: |
59592607 |
Appl. No.: |
16/626663 |
Filed: |
June 28, 2018 |
PCT Filed: |
June 28, 2018 |
PCT NO: |
PCT/GB2018/051805 |
371 Date: |
December 26, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02E 10/30 20130101;
F03B 13/1865 20130101; F03B 13/20 20130101; F03B 13/1885 20130101;
F05B 2270/18 20130101 |
International
Class: |
F03B 13/18 20060101
F03B013/18 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 30, 2017 |
GB |
1710550.3 |
Claims
1. A generator for converting wave motion in a body of water to
useful energy, the generator comprising: at least one energy
capturing float which is movable in response to said wave motion; a
reaction member to be positioned below the energy capturing float;
connection means for connecting said at least one energy capturing
float to said reaction member; energy conversion means for
converting relative movement between said reaction member and said
at least one respective energy capturing float to the useful
energy; wherein the generator includes adaptable depth setting
means for setting, over a predetermined range, the depth of the
reaction member in the body of water and the height of the reaction
member from a bed of the body of water, characterised in that both
the float and the reaction member have a positive buoyancy.
2. A generator as claimed in claim 1, wherein the connecting means
defines a distance between said energy capturing float and said
reaction member.
3. A generator as claimed in claim 2, wherein the connection means
are of adjustable length for independently adjusting the distance
between the energy capturing float and the reaction member.
4. A generator as claimed in claim 1, claim 2, or claim 3, wherein
the positive buoyancy of the float and the reaction member cause
adequate tension in the depth setting means to provide stability to
the reaction member when submerged.
5. A generator as claimed in claims 1 to 4, in which the connection
means comprise at least one flexible line of adjustable length in
which the length adjustment is achieved by winding the or each
flexible line around a respective drum.
6. A generator as claimed in claims 1 to 5, in which the connection
means are adjustably mounted to the reaction member such that the
geometry of the connection means can be altered.
7. A generator as claimed in any one of claims 1 to 6, wherein the
depth setting means comprise at least one flexible mooring line of
adjustable length to adjustably position the reaction member above
the bed of the body of water.
8. A generator as claimed in claim 7, wherein the generator has a
net positive buoyancy that is resisted by tension of the at least
one flexible mooring line.
9. A generator as claimed in any one of claims 1 to 8, wherein the
depth setting means is coupled to the reaction member by a
winch.
10. A generator as claimed in any one of claims 1 to 9, wherein at
least one of: a. the reaction member length; b. the reaction member
width; c. the reaction member diameter; is selected from the range
20 to 60 metres.
11. A generator as claimed in any one of claims 1 to 10, wherein at
least one of: a. the float diameter; b. the float length; c. the
float width; is selected from the range 10 to 20 metres.
12. A generator as claimed in any one of claims 1 to 11, wherein
the separation between the float and the reaction member is
selected from the range 0 to 50 metres.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to generators that can be used
to extract energy from waves in a body of water, by converting the
wave energy to more readily usable energy.
BACKGROUND TO THE INVENTION
[0002] In recent years, there has been increased emphasis on the
need to exploit renewable energy so that it significantly
contributes to global energy production. A combination of
government targets, media representation of the issues associated
with non-renewable energy sources, and ever increasing energy costs
have all created a powerful driving force for the development of
renewable energy systems.
[0003] Negative impacts of fossil fuels on our environment are well
known, as are the problems and high costs associated with nuclear
energy. Harnessing of the huge natural abundance of renewable
energy on the other hand is constrained merely by our capability of
capturing and supplying it at an economically viable price.
[0004] One potential renewable energy source is wave power--an
abundant and consistent energy resource available in all of the
world's large oceans and seas. Various wave devices for generating
energy from wave power have been proposed, but such devices have
many limitations with no one device having the proven ability to
reliably exploit the available wave power resource over the long
term.
[0005] We have disclosed in WO2010007418, WO2011158006 and
WO2013068748 successively improved generators for converting wave
motion to useful energy. The generators disclosed use a submersible
reaction body to solve many of the difficulties associated with
existing wave energy converters.
[0006] However, the wave energy converters disclosed in
WO2010007418, WO2011158006 and WO2013068748 still have potential
for further improvement.
SUMMARY OF THE INVENTION
[0007] In accordance with the invention, a generator is provided as
outlined in the accompanying claims.
[0008] The generator of the present invention is for converting
wave motion in a body of water to useful energy, the generator
comprising: at least one energy capturing float which is movable in
response to said wave motion; a reaction member to be positioned
below the energy capturing float; connection means for connecting
said at least one energy capturing float to said reaction member;
energy conversion means for converting relative movement between
said reaction member and said at least one respective energy
capturing float to the useful energy; wherein the generator
includes adaptable depth setting means for setting, over a
predetermined range, the depth of the reaction member in the body
of water and the height of the reaction member from a bed of the
body of water; characterised in that both the float and the
reaction member have a positive buoyancy.
[0009] With reference to the prior art, the apparatus described and
illustrated in WO2010007418 has an energy capturing float that
remains on the sea surface continuously, all the time. This means
that in highly energetic sea conditions, such as storms, the float
will be subject to high loads. These high loads must be managed by
the structure and the power take-off system, resulting in costly
over-engineering of the apparatus.
[0010] The apparatus described and illustrated in WO2011158006 and
WO2013068748 provide improvements over this, however the stability
of the submerged reaction member is limited by the mass and
therefore size of the reaction member, and therefore is
significantly variable across the range of conformations disclosed
in WO2011158006 and WO2013068748.
[0011] We have now devised a generator for converting wave motion
in a body of water to useful energy, the generator having positive
buoyancy in both the reaction member and the energy capturing float
to increase the stability of the reaction member in response to
forces exerted on it both directly by the waves and indirectly
through forces transferred to it by the power capturing float.
[0012] Our simulation work has shown that by increasing the
buoyancy of the reaction member it is possible to transfer more of
the reaction forces to the seabed and therefore increase the
stability of the reaction member, particularly in energetic sea
states. A further advantage of increasing the utilisation of the
seabed for reaction purposes is that the size and mass of the
reaction member can be reduced at the same time as the stability is
improved.
[0013] The known generator described in the abovementioned
WO2013068748 comprises: at least one energy capturing float which
is movable in response to said wave motion; a reaction member to be
positioned below the energy capturing float; connection means for
connecting said at least one energy capturing float to said
reaction member and defining a distance between said energy
capturing float and said reaction member; energy conversion means
for converting relative movement between said reaction member and
said at least one respective energy capturing float to the useful
energy; wherein the generator includes adaptable depth setting
means for setting, over a predetermined range, the depth of the
reaction member in the body of water and the height of the reaction
member from a bed of the body of water, and in that the connection
means are of adjustable length for independently adjusting the
distance between the energy capturing float and the reaction
member.
[0014] Any reference herein to known prior art does not, unless the
contrary indication appears, constitute an admission that such
prior art is commonly known by those skilled in the art to which
the invention relates, at the priority date of this
application.
[0015] Preferably the connecting means defines a distance between
said energy capturing float and said reaction member. Most
preferably, the connection means are of adjustable length for
independently adjusting the distance between the energy capturing
float and the reaction member.
[0016] The generator preferably includes adaptable setting means
for setting, over a predetermined range, the depth of the reaction
member in the body of water. The setting means further is arranged
to set the height of the reaction member from the bed of the body
of water.
[0017] By "setting the depth" we mean controlling in a manner
whereby the precise depth can be chosen and fixed in a modifiable
manner. In other words, if it is wished to change the set depth,
the setting means may be adapted, modified and controlled such that
a further precise depth can be chosen and fixed.
[0018] In a first embodiment of the invention, the depth setting
means comprise at least one flexible mooring line of adjustable
length to adjustably secure the reaction member to a bed of the
body of water. In this embodiment, the generator has a net positive
buoyancy that is resisted by tension of the flexible mooring
line(s).
[0019] The angle at which the mooring lines are positioned relative
to the bed of the body of water can be changed to optimise the
stability of the reaction body. A desirable angular configuration
of the mooring lines is vertical in the water column, i.e. straight
down from the reaction body to the bed of the body of water.
[0020] In the above-mentioned embodiment, the depth setting means
is preferably coupled to the reaction member by one or more
winches.
[0021] Preferably, the connectors in the generator according to the
invention include at least one flexible line, which is of
adjustable length, the length adjustment being typically achieved
by winding the or each line around a respective drum. Thus the
distance between the reaction member and the energy capturing float
can be adjusted by winding the connector lines on or off the
respective drums.
[0022] In preferred embodiments of the invention the connectors are
of adjustable length so as to permit independent adjustment of the
distance (or spacing in a vertical direction) between the energy
capturing float and the reaction member, and therefore the depth of
the energy capturing float in the body of water.
[0023] Furthermore, it is preferred that the reaction member has
adjustable buoyancy and a plurality of buoyancy modes, including at
least one submerged operating mode in which the reaction member and
buoyancy float are submerged using the depth setting means, and a
maximum buoyancy mode in which the reaction member floats on the
surface of the body of water. In any of these plurality of buoyancy
modes, the reaction member should have inertia and drag to resist
potential movement of the energy capturing float caused by the wave
motion.
[0024] Reaction member width and/or can be selected to provide
maximum stability and may relate proportionally to float diameter,
width and/or length. In preferred embodiments, the reaction member
length and/or width is selected from the range 30 to 50 metres,
where a float diameter, width and/or length is selected from
between 10 metres and 20 metres. Most preferably, the reaction
member width and/or length is 40 metres and the float diameter,
width and/or length is 15 metres. At this approximate ratio,
optimum stability is provided for the reaction member within the
water. Positive buoyancy of both the reaction member and the float
provide adequate tension on the mooring lines of the depth setting
means, which in turn also confers an optimum level of stability
upon the generator within the water.
[0025] The separation between the float and the reaction member is
also critical to the stability of the generator, particularly in
highly energetic sea conditions wherein the generator is subjected
to powerful wave forces. An optimum separation distance between the
reaction member and the float is preferably selected from the range
20 to 40 metres. Most preferable embodiments comprise a separation
between the float and the reaction member of 30 metres.
[0026] Preferred embodiments of the invention will now be described
in more detail, with reference to the accompanying drawings, in
which like parts are denoted by like reference numerals throughout.
In order to avoid detracting from the clarity of the drawings, not
all parts are labelled in all drawings.
DETAILED DESCRIPTION
[0027] Specific embodiments will now be described by way of example
only, and with reference to the accompanying drawings, in
which:
[0028] FIG. 1 is a perspective view of a preferred embodiment of
wave generator according to the invention when on the surface of a
body of water (generally, the sea);
[0029] FIG. 2 is a perspective view of the wave generator of FIG. 1
when submerged beneath the surface of that body of water; and
[0030] FIG. 3 is an orthogonal view showing the energy convertor of
FIG. 2 moored to the bed of the body of water.
[0031] Referring first to FIG. 1 and FIG. 2, there is shown an
exemplary wave powered generator according to the invention which
comprises a submersible subsea reaction member 1; an energy
capturing float 2 that moves in response to the waves; a series of
energy converters 6a, 6b, 6c, 6d mounted on the reaction member 1;
and respective connecting lines 5a, 5b, 5c, 5d of adjustable length
that connect the energy capturing float 2 to the respective energy
converter 6a, 6b, 6c, 6d.
[0032] In FIG. 1, each of the connecting lines 5a, 5b, 5c, 5d is
wound around a drum on the respective energy converter 6a, 6b, 6c,
6d to the fullest or maximum extent such that the spacing between
the energy capturing float 2 and the reaction member 1 is at a
minimum. In this case the reaction member 1 and the energy
capturing float 2 are together floating on the surface S of a body
of water.
[0033] Conversely, in the arrangement shown in FIG. 2, each of the
connecting lines 5a, 5b, 5c, 5d is let out (wound around the
respective drum) such that the spacing between the energy capturing
float 2 and the reaction member 1 is at a maximum. In this case,
the energy capturing float 2 is shown just below the surface S of
the body of water.
[0034] FIG. 2 and FIG. 3 show the wave energy generator with
mooring lines 3a, 3b, 3c, 3d which tether the generator to the
seabed SB, thereby keeping the generator on station.
[0035] The mooring lines 3a, 3b, 3c, 3d may be connected to the
reaction body 1 via corresponding length adjusting means 4a, 4b,
4c, 4d to enable the depth of submersion of the reaction member 1
to be varied.
[0036] It should be noted that in the first embodiment of the
invention the mooring lines 3a, 3b, 3c, 3d remain tensioned at all
times so that the generator cannot move freely up and down in the
water column. The positive buoyancy of the reaction member 1 and
the float 2, B2 and B1 respectively, enables the reaction member 1
to place upon the mooring lines 3a, 3b, 3c, 3d a tension Ta, Tb,
Tc, Td, providing stability to the reaction member 1 and the float
2 in highly energetic sea conditions.
[0037] In the embodiment shown, the float has a radius R of 7.5
metres (diameter of 15 metres) and the reaction member has a length
and width L of 40 metres. The separation from the float 1 and the
reaction member 2 is a distance D2 of 30 metres. In this
configuration the generator is arranged to perform optimally in an
open sea environment.
[0038] The reaction member 1 is generally of a hollow construction
and is adapted to be selectively filled with air or water to adjust
its buoyancy. The wave powered generator according to the invention
has a positive net buoyancy comprising the buoyancy of the reaction
member 1, B2 and the buoyancy of the energy capturing float 2, B1.
The generator has a permanent positive buoyancy, but may comprise a
surface configuration as shown in FIG. 1 and a submerged
configuration as shown in FIG. 2 and FIG. 3. The submerged
configuration is the result of the mooring lines 3a, 3b, 3c, 3d
used as a depth setting means.
[0039] When in the surface configuration (FIG. 1), the reaction
member 1 floats on the surface S of the body of water (such as the
sea) with sufficient buoyancy for it to carry all other components
of the apparatus. In this condition the generator according to the
invention can be readily disconnected from the mooring lines 3a,
3b, 3c, 3d and transported across the surface S of the body of
water. The wave powered generator can sit sufficiently high in the
water that all connections to mooring lines 3a, 3b, 3c, 3d and
power umbilical 7 can be clear of the water and be easily
accessible. The wave powered generator can also create its own
stable service platform with all serviceable components clear of
the water to enable easy access for maintenance.
[0040] With reference to FIG. 2, when the wave generator is in the
submersed operating configuration, the buoyant reaction member 1 is
held suspended by the combination of the energy capturing float 2
and the mooring lines 3a, 3b, 3c, 3d. The net buoyancy of the
generator is defined by the sum of the buoyancy values of the
reaction member 1 and the energy capturing float 2 (B1+B2).
[0041] The reaction member 1 has a large mass that resists
movements caused to it by the forces applied by the float 2 via the
connecting lines 5a, 5b, 5c, 5d, and by the forces applied to it
directly by the waves. The reaction member 1 also has a large
surface area perpendicular to the direction of the heave force,
which thereby provides further resistance to movement by way of a
large drag and added mass.
[0042] The reaction member 1 may be held suspended between the
energy capturing float 2 and the seabed SB using the mooring lines
3a, 3b, 3c, 3d at a depth D1 sufficient to ensure that the reaction
member 1 is generally below the influence of waves on the sea
surface. Therefore movement of the energy capturing float 2 caused
by waves results in relative motion between the energy capturing
float 2 and the reaction member 1. This movement is taken up by
respective working strokes of the energy converters 6a, 6b, 6c, 6d
and thus exploited to produce power.
[0043] In the illustrated embodiment, a single float 2 is shown,
but it will be understood that more than one such float can be
provided if appropriate, each with its own series of energy
converters mounted on the reaction member 1, together with
respective connecting lines.
[0044] In the described embodiments, the float radius is shown as
7.5 metres (diameter 15 meters) and the length and width of the
reaction member are shown as 40 metres. Alternative embodiments may
comprise a float which can be of any shape with a diameter, or
width and/or length, of between 10 metres and 20 metres.
Alternative embodiments may also comprise a reaction member of any
shape, with length and/or width, or diameter (where spherical), of
between 20 metres and 40 metres.
* * * * *